Do similar bonus in combat stack with each other to give you a larger bonus to your roll? For example in ship combat would having Murder-Servitors, Teleportarium and a Barracks give you a total of +60 to command checks for Hit and Runs, as each gives a +20 bonus. Or would it be more in line to have these do three different Hit and Run attacks each turn with a +20 to each one?

Bonuses stacked in Dark Heresy so I imagine that they would here as well, including for ship combat.

I believe you can't go over +60 or below -60 for bonuses.

Yep, although if there are lots of modifiers in play, the additional bonuses and penalties factor into the final math. So if you had a +80 to hit in bonuses, but also -30 in penalties, it would work out to +50, for example.

It's +/-60? I thought it was total could not exceed +/-30. Whoops. My players are going to be pissed.